Methane sources in arctic thermokarst lake sediments on the North Slope of Alaska. Issue 2 (22nd January 2015)

• Record Type: Journal Article
• Authors: Matheus Carnevali, P. B.; Rohrssen, M.; Williams, M. R.; Michaud, A. B.; Adams, H.; Berisford, D.; Love, G. D.; Priscu, J. C.; Rassuchine, O.; Hand, K. P.; Murray, A. E.
• Is Part Of: Geobiology. Volume 13:Issue 2(2015)
• Page Start: 181
• Page End: 197
• Publication Date: 2015-01-22
• Subjects: Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Ecology -- Periodicals; 551
• DOI: 10.1111/gbi.12124
• Languages: English
• ISSNs: 1472-4677

Abstract

<abstract abstract-type="main" id="gbi12124-abs-0001"> <title>Abstract</title> <p>The permafrost on the North Slope of Alaska is densely populated by shallow lakes that result from thermokarst erosion. These lakes release methane (CH<sub>4</sub>) derived from a combination of ancient thermogenic pools and contemporary biogenic production. Despite the potential importance of CH<sub>4</sub> as a greenhouse gas, the contribution of biogenic CH<sub>4</sub> production in arctic thermokarst lakes in Alaska is not currently well understood. To further advance our knowledge of CH<sub>4</sub> dynamics in these lakes, we focused our study on (i) the potential for microbial CH<sub>4</sub> production in lake sediments, (ii) the role of sediment geochemistry in controlling biogenic CH<sub>4</sub> production, and (iii) the temperature dependence of this process. Sediment cores were collected from one site in Siqlukaq Lake and two sites in Sukok Lake in late October to early November. Analyses of pore water geochemistry, sedimentary organic matter and lipid biomarkers, stable carbon isotopes, results from CH<sub>4</sub> production experiments, and copy number of a methanogenic pathway‐specific gene (<italic>mcrA</italic>) indicated the existence of different sources of CH<sub>4</sub> in each of the lakes chosen for the study. Analysis of this integrated data set revealed that there is biological CH<sub>4</sub> production in Siqlukaq at moderate levels, while the very low levels of CH<sub>4</sub> detected in Sukok had a mixed origin, with little to no biological CH<sub>4</sub> production. Furthermore, methanogenic archaea exhibited temperature‐dependent use of <italic>in situ</italic> substrates for methanogenesis, and the amount of CH<sub>4</sub> produced was directly related to the amount of labile organic matter in the sediments. This study constitutes an important first step in better understanding the actual contribution of biogenic CH<sub>4</sub> from thermokarst lakes on the coastal plain of Alaska to the current CH<sub>4</sub> budgets.</p> </abstract>